This application is based on application No. 10-133585 filed in Japan, the contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a remote diagnostic system constituted of a computer having means for enabling communication of data, and a plurality of terminals having means for enabling communication of data, for making a remote diagnosis for each device by periodically communicating the state of the device using the computer.
2. Description of the Related Art
A conventionally known remote diagnostic system periodically makes communication between a terminal connected to a device and a remote diagnostic unit to make a remote diagnosis for the device periodically. In general, the public telephone line is utilized for communication between the terminal and the remote diagnostic unit. The following two methods have been devised for connecting the terminal with the public telephone line.
(1) Allocating a dedicated line to the terminal:
An advantage of this method is in that the starting time of communication and the communication period are not limited since the terminal is connected with the dedicated line, while a disadvantage thereof is the cost of the work required for installing the dedicated line.
(2) Allocating an existing line to the terminal:
The terminal is connected as a branch machine to a base machine connected to the existing line. According to this method, the necessary work is just interconnection between the base machine and the terminal. Therefore, this method is advantageously inexpensive since the work for installing the dedicated line is unnecessary. However, a problem arises when the remote diagnostic unit attempts to apply a trigger to the terminal for starting communication. If the base machine is a telephone set, for example, the trigger causes the telephone set to ring (corresponding to call) and the user may take up its handset. As a result, communication between the remote diagnostic unit and the terminal cannot be started. Accordingly, a disadvantage of this method is in that only the terminal (branch machine) can apply the trigger for starting communication.
Two methods listed below have been devised for applying a trigger to start communication between the remote diagnostic unit and the terminal.
(1) Applying a trigger by the remote diagnostic unit:
If there are a plurality of terminals that should communicate with the remote diagnostic unit, this method allows the remote diagnostic unit to make a schedule. For example, if any device connected to one of the terminals fails, an emergency communication from the terminal interrupts in the remote diagnostic unit. An advantage of this method in this case is in that the schedule can easily be arranged again. However, if the terminal is connected to the base machine as a branch machine, the call for communication is inconveniently supplied not only to the branch machine but to the base machine. Further, if the terminal is busy, communication is impossible and the second call have to be made. The busy state of the terminal refers to the state in which the terminal is a copying machine and the copying machine is in use for making copies, for example.
(2) Applying a trigger by the terminal:
An advantage of this method is in that communication is possible without affecting a base machine when the terminal is connected as a branch machine to the base machine. A further advantage is in that when the terminal is busy at a communication time which is preliminary allocated to the terminal, or when the base machine uses the line at that time, communication can be started after the terminal temporarily ends the busy state or after detection of termination of the communication by the base machine. However, in order to make communication with the remote diagnostic unit, the starting time of the communication should be allocated to each terminal and the time should be input for storing the allocated time in each terminal, requiring the user operating the terminal to perform a troublesome work. In addition, the terminal cannot make communication with the remote diagnostic unit when an emergency communication from another terminal interrupts in the remote diagnostic unit, and the need of redialing occurs.
The conventional system employs the public telephone line, so that the user needs to interconnect a telephone switching unit with the terminal, leading to an additional cost. Depending on the length of the interconnection, the range in which the terminal can be located is fixed to considerably limit the location of the terminal when the arrangement of office furniture is to be changed. In some cases, the interconnection must be made again for moving the terminal.
The present invention has been made for solving the problems above. One object of the present invention is to provide a remote diagnostic system capable of selecting a method of communication considering the difference in environment of terminals connected to a computer.
Another object of the invention is to provide a remote diagnostic system capable of preventing an inconvenience of occurrence of a call to a base machine when a terminal is a branch machine of the base machine, and accordingly reducing the rate of occurrence of redialing to achieve timely communication of information.
Further object of the invention is to provide a remote diagnostic system which does not require interconnection between a telephone switching unit and a terminal and thus provides a wide freedom of location of the terminal.
In order to achieve the above objects, according to one aspect of the invention, a remote diagnostic system includes a computer having means for enabling transmission and reception of data, and a plurality of terminals each having means for enabling transmission and reception of data. In the remote diagnostic system, the computer diagnoses respective devices connected to respective terminals by transmitting and receiving data to and from the plurality of the terminals at a prescribed time interval.
The plurality of terminals include a first group of at least one terminal which receives from the computer a start signal for starting transmission and reception of data, and a second group of at least one terminal which transmits to the computer the start signal for starting transmission and reception of data.
According to another aspect of the invention, a terminal is connected to a device and transmits a state of the device to a computer by transmitting and receiving data to and from the computer. The terminal includes communication means for transmitting and receiving data to and from the computer, clock means for measuring time, and means for setting a prescribed time. The communication means transmits a start signal to the computer for starting transmission and reception of data when the measurement of the clock means indicates the set prescribed time. The prescribed time is included in the data transmitted from the computer.
According to a further aspect of the invention, a computer diagnoses devices connected respectively to a plurality of terminals by transmitting and receiving data to and from the plurality of terminals. The computer includes communication means for transmitting and receiving data to and from the terminals, clock means for measuring time, means for setting a first time and a second time, first communication starting means for transmitting to the terminals a start signal for enabling the communication means when the measurement of the clock means indicates the first time, second communication starting means for enabling the communication means when the second communication means receives from the terminals a start signal for starting transmission and reception of data, and time transmitting means for transmitting the second time to the terminals when the communication means is enabled by the second communication starting means.
The invention above is thus effective in that it is possible to select a communication method considering difference in environment of the terminals connected to the computer. The invention is further effective in that it is possible to prevent an inconvenience of occurrence of a call to a base machine when a terminal is a branch machine of the base machine and accordingly reduce the rate of occurrence of redialing, and consequently, the information can timely be transmitted and received. In addition, the invention is effective in that interconnection between a telephone switching unit and a terminal is unnecessary owing to use of radio, and thus a wide freedom of location of the terminal is achieved.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.